Asriel Dreemurr, the new king of the monsters. Although many think he is too young to be ruler, he leads his subjects respectively, using his parents as personal advisors.
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In his past, Asriel was simply a young child, born to Toriel and Asgore Dreemurr: the king and queen of the old Dreemurr Kingdom. After the events preceding the arrival of Frisk, however, Asriel's soul was seemingly destroyed. Long before Frisk arrived in the underground, Asriel's soul had been reincarnated by the king's personal scientist, Alphys. Using a concentrated synthetic Determination, Asriel was reborn as Flowey, a sinister, emotionless flower with the power to save and reset the world at will, much like Frisk. After an epic final battle, in which Flowey absorbs the souls of all monsters at once and is reborn as God of Hyperdeath, Asriel is spared by Frisk and regains his emotions for a moment, long enough for him to spare Frisk and use his newfound power to shatter the barrier that was sealing the underground from the surface, releasing the monsters from their captivity. Asriel then converted back to Flowey, but without his ability to manipulate the timeline.
Several years later, upon the discovery that Asriel's true soul was still floating deep inside Flowey's own determination, Alphys and a group of human scientists were able to run an experiment that rejoined Asriel's original soul, and split it from Flowey's. Asriel was successfully revived, in his fully grown form, and returned to the kingdom where his duties, and family, were waiting. Flowey was kept in solitary confinement, only to be visited by Frisk and Asriel himself.
After the retirement of king Asgore, the crown was passed on to Asriel, and the duties of running the new surface kingdom along with it. Asriel now faces growing tension between his own kingdom and a neighboring human colony that hold a prejudice of monsters.
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Asriel has many powers, and if pushed to assume his hyperdeath form, can release massive bursts of magic energy from his paws, and use various forms of magic. While in hyperdeath form, he also gains a pair of huge, ethereal wings, with which he can fly at lightning fast speeds, and maneuver better. This, paired with his dual swords, make him a powerful opponent.
Asriel's main weakness is his remaining innocence. Not used to the new world, Asriel is still a shy boy inside, and therefore has trouble grasping his new adult responsibilities. This, paired with a fear for losing the ones he loves, can be used against him with powerful mental results. Asriel is also not immortal, even in his hyperdeath form. He can still be injured, and can still suffer death.